Pulmonary involvement in patients with thrombotic thrombocytopenic purpura.

Objectives: To determine the frequency of pulmonary involvement in patients with thrombotic thrombocytopenic purpura (TTP).

Methods: The experience of the Oklahoma TTP-HUS (hemolytic-uremic syndrome) Registry, a population-based cohort of consecutive patients without selection or referral bias, 1995-2012, was analyzed. Evidence for pulmonary involvement in patients with TTP was also documented with a systematic review of published reports.

Results: Only one of 74 Registry patients with acquired severe ADAMTS13 deficiency (activity <10%) had clinically important pulmonary involvement (transient PaO2 , 42 mm Hg; arterial O2 saturation, 78%; normal chest X-ray). No clinically important pulmonary involvement occurred in the remaining 73 patients. The systematic review identified 144 articles with search terms for TTP and pulmonary involvement; seven, published 1978-2002, had evaluable individual patient data. Five articles described single patients; only one patient was documented to have severe acquired ADAMTS13 deficiency; in none of the five patients was pulmonary involvement clearly related to TTP. Two articles were case series of seven patients each; no patients had ADAMTS13 activity measured. Each of the 14 patients had potential etiologies other than TTP for pulmonary involvement.

Conclusions: Only one of 74 patients in the Oklahoma Registry had clinically important pulmonary involvement. A systematic review of published reports documented no clear evidence for pulmonary involvement resulting from TTP. Clinically important pulmonary involvement may be rare in patients with TTP because (i) pulmonary microvasculature may be inherently resistant to the formation of platelet thrombi and (ii) pulmonary function can be maintained in spite of multiple microvascular thrombi.